A obtenção da sílica vítrea pelo processo de sinterização por plasma pulsado (SPS), a partir de matérias-primas de diferentes estruturas (cristalina e amorfa) e diferentes granulometrias, foi investigada. Análises de difração de raios X, transmitância óptica, microscopia óptica e eletrônica de varredura, e medições de densidade foram realizadas nas amostras sinterizadas. Sílicas vítreas transparentes foram fabricadas a partir de pós de quartzo atingindo-se temperaturas finais entre 1450 e 1600°C, enquanto que nanopó e pó amorfo de sílica formaram consolidados transparentes com temperaturas máximas próximas de 1200° C. Taxas de aquecimento entre 40 e 150°C/min. foram utilizadas nas sinterizações, com tempos de processo menores que 40 minutos. As maiores taxas de aquecimento exigiram uma maior temperatura final para a fusão completa do material cristalino e causaram, de forma indireta, a presença de aglomerações de micro-bolhas nas amostras obtidas com o nanopó. Um gradiente radial de temperatura (decrescente do centro para as bordas) foi observado nos consolidados fabricados com os pós cristalinos, facilitando o processo de fechamento da porosidade aberta. A presença ou ausência de material não fundido e de bolhas nas amostras foram analisadas por difratogramas de raios X, microscopia óptica e medidas de densidade. A análise da transmitância indicou uma quantidade praticamente nula de grupos OH nos compactos sinterizados com os pós cristalinos e em torno de 20 ppm no caso dos sólidos fabricados com matéria-prima sol-gel. Amostras de nanopós de sílica dopada com titânia (~6% em massa) foram processadas com temperaturas finais de 1200 e 1400°C apresentando coloração azulada e negra, respectivamente, e aumento dos clusters de titânia para a temperatura mais elevada. A sinterização a uma temperatura em torno 1200°C mantida por apenas 4 minutos resultou na conversão completa da fase anatase para a fase rutilo da titânia. / The production of vitreous silica by the spark plasma sintering (SPS) process, starting from raw materials of different structures (crystalline and amorphous) and granulometry were investigated. Analysis of X-ray diffraction, optical transmittance, optical and scanning electron microscopy, and density measurements were performed on the sintered compacts. Transparent vitreous silica was fabricated from quartz powder at final temperatures ranging from 1450 and 1600°C while silica nanopowder and silica powder formed transparent compacts at temperatures around 1200°C. Heating rates between 40 and 150° C/min. were used in processes with durations smaller than 40 minutes. Higher heating rates demanded higher final temperatures to complete the fusion process and caused, indirectly, the formation of micro-bubbles agglomerations in the samples produced from the nanopowder. A radial gradient of temperature (decreasing from the center to the border) was observed at the compacts fabricated with the crystalline powders favoring the closure of the open porosity. The presence or the absence of non-fused material and bubbles in the samples was analyzed by X-ray diffraction, optical microscopy and density measurements. The transmittance analysis indicated an almost zero quantity of OH groups in the compacts sintered from crystalline powders and about 20 ppm in the solids fabricated from the sol-gel raw material. Nanopowder samples of silica titania (~6 wt % of titania) were processed with final temperatures of 1200°C and 1400°C presenting blue and black coloration, respectively, and an increase of the titania clusters for the highest temperature. The sintering at temperatures near 1200°C with a holding time of just 4 minutes caused the complete anatase-rutile conversion in titania.

Orientador: Darcy Hiroe Fujii Kanda / Banca: Luiz Francisco Malmonge / Banca: Dante Luis Chinaglia / Resumo: Compósitos poliméricos condutores, também chamados de polímeros condutores extrínsecos, têm sido alvo de intensa pesquisa científica devido ao seu grande potencial de aplicação nos mais diversificados setores industriais. Esses materiais combinam as características de um polímero (leveza, flexibilidade, fácil processamento) com as de cargas condutoras (alta condutividade). O poliuretano derivado de óleo de mamona (PUR) é um polímero obtido pela mistura de pré-polímero e poliol (derivado de óleo de mamona) que apresenta grande potencial para ser utilizado como matriz polimérica em compósitos. Ele possui propriedades equivalentes aos dos poliuretanos (PU) convencionais e tem como vantagem ser um polímero biodegradável e proveniente de fonte renovável. Em relação às cargas condutoras, o negro de fumo (NF) é um dos materiais mais utilizados para esse fim, enquanto que pouco se encontra na literatura sobre o carvão ativado nano em pó (CANP), mesmo possuindo estrutura semelhante e maior condutividade que o NF. Neste contexto, o presente trabalho tem como objetivo viabilizar os processos de síntese e fazer a caracterização elétrica dos compósitos poliuretano derivado de óleo de mamona/carvão ativado nano em pó (PUR/CANP) e poliuretano derivado de óleo de mamona/negro de fumo (PUR/NF) na forma de filmes pelo método "casting", mantendo fixa a razão pré-polímero/poliol e variando a fração de volume de CANP e NF. A análise térmica foi feita por Calorimetria Diferencial de Varredura (DSC), o estudo da condutividade dc e ac foram feitas pelo Método de Duas Pontas (tensão x corrente) (MDP) e pela técnica de Espectroscopia de Impedância Elétrica (EIE), respectivamente, e a análise morfológica foi feita em Microscópio Eletrônico de Varredura com canhão de elétrons por... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Conductive polymer composites, also called extrinsic conducting polymers, has been the subject of intense scientific research due to its great potential for industrial application. These materials combine the characteristics of a polymer (lightness, flexibility, easy processing) with the conductive fillers (high conductivity). The castor oil based polyurethane (PUR) is a polymer obtained from pre-polymer and polyol (based castor oil) mixing which has great potential to be used as matrix polymer in composites. It has properties equivalent to those of conventional polyurethane (PU) and has the advantage of being a biodegradable polymer and from a renewable source. In relation to conductive fillers, carbon black (CB) is one of the most widely used materials for this purpose, while in the literature there are few data about activated carbon nanopowder (ACNP), despite having similar structure and that the higher conductivity than CB. In this context, this work aims to provide the synthesis processes and electrically characterize of composite castor oil based polyurethane/activated carbon nanopowder (PUR/ACNP) and castor oil based polyurethane/carbon black (PUR/CB) in the form of films by casting, keeping the ratio pré-polímero/poliol fixed and varying the volume fraction ACNP and CB. The sample were characterized using Differential Scanning Calorimetry (DSC), Two Points Method (voltage x current) (TPM), Electrical Impedance Spectroscopy (EIS) and Scanning Electron Microscope with electron gun for field emission (FEG-SEM). DSC results showed that the glass transition temperature (Tg) of composites do not depend of type or volume fraction of conductive fillers. The results of electrical analysis showed that the samples of PUR/CB have lower percolation threshold than those of PUR/ACNP (20% vs. 40%). This result is due the distribution... (Summary complete electronic access click below) / Mestre

In this work, a broad range of analytical methods was applied to the study of the following three materials systems: yttria-stabilised zirconia (YSZ), samarium-doped ceria (SDC) and SDC-supported metal catalysts. YSZ and SDC were studied in the light of their application as solid electrolytes in Solid Oxide Fuel Cells. The SDC-supported metal catalysts were evaluated for application in the reforming of methanol. The conductive properties of YSZ pellets derived from powders of different Y contents and particle size ranges were investigated using Impedance Spectroscopy (IS). Comparative studies of the crystallography (by X-ray Powder Diffraction (XRD)), morphology (by Scanning and Transmission Electron Microscopy (SEM, TEM)), chemical composition (by Energy Dispersive X-ray Spectroscopy (EDX) and Inductively Coupled Plasma Mass Spectroscopy (ICP-MS)) and sintering behaviour (dilatometry) were employed in the overall assessment of the conductivity results collected. Detailed studies of three SDC compositions were performed on nanopowders prepared by a low temperature method developed in the Baker group. Modifications led to a simple and reliable method for producing high quality materials with crystallites of ~10 nm diameter. The products were confirmed by XRD and TEM to be single-phase materials. Thermogravimetric analysis, dilatometry, specific surface area determination, elemental analysis and IS were carried out on these SDC powders. The relationships between particle size, chemical composition, sintering conditions and conductivity were studied in detail allowing optimum sintering conditions to be identified and ionic migration and defect association enthalpies to be calculated. Finally, the interesting results obtained for the SDC nanopowders were a driving force for the preparation of SDC-supported metal catalysts. These were prepared by three different methods and characterised in terms of crystallographic phase, specific surface area and bulk and surface chemical composition. Isothermal catalytic tests showed that all catalysts had some activity for the reforming of methanol and that some compositions showed both very high conversions and high selectivities to hydrogen. These catalysts are of interest for further study and possibly for commercial application.

A obtenção da sílica vítrea pelo processo de sinterização por plasma pulsado (SPS), a partir de matérias-primas de diferentes estruturas (cristalina e amorfa) e diferentes granulometrias, foi investigada. Análises de difração de raios X, transmitância óptica, microscopia óptica e eletrônica de varredura, e medições de densidade foram realizadas nas amostras sinterizadas. Sílicas vítreas transparentes foram fabricadas a partir de pós de quartzo atingindo-se temperaturas finais entre 1450 e 1600°C, enquanto que nanopó e pó amorfo de sílica formaram consolidados transparentes com temperaturas máximas próximas de 1200° C. Taxas de aquecimento entre 40 e 150°C/min. foram utilizadas nas sinterizações, com tempos de processo menores que 40 minutos. As maiores taxas de aquecimento exigiram uma maior temperatura final para a fusão completa do material cristalino e causaram, de forma indireta, a presença de aglomerações de micro-bolhas nas amostras obtidas com o nanopó. Um gradiente radial de temperatura (decrescente do centro para as bordas) foi observado nos consolidados fabricados com os pós cristalinos, facilitando o processo de fechamento da porosidade aberta. A presença ou ausência de material não fundido e de bolhas nas amostras foram analisadas por difratogramas de raios X, microscopia óptica e medidas de densidade. A análise da transmitância indicou uma quantidade praticamente nula de grupos OH nos compactos sinterizados com os pós cristalinos e em torno de 20 ppm no caso dos sólidos fabricados com matéria-prima sol-gel. Amostras de nanopós de sílica dopada com titânia (~6% em massa) foram processadas com temperaturas finais de 1200 e 1400°C apresentando coloração azulada e negra, respectivamente, e aumento dos clusters de titânia para a temperatura mais elevada. A sinterização a uma temperatura em torno 1200°C mantida por apenas 4 minutos resultou na conversão completa da fase anatase para a fase rutilo da titânia. / The production of vitreous silica by the spark plasma sintering (SPS) process, starting from raw materials of different structures (crystalline and amorphous) and granulometry were investigated. Analysis of X-ray diffraction, optical transmittance, optical and scanning electron microscopy, and density measurements were performed on the sintered compacts. Transparent vitreous silica was fabricated from quartz powder at final temperatures ranging from 1450 and 1600°C while silica nanopowder and silica powder formed transparent compacts at temperatures around 1200°C. Heating rates between 40 and 150° C/min. were used in processes with durations smaller than 40 minutes. Higher heating rates demanded higher final temperatures to complete the fusion process and caused, indirectly, the formation of micro-bubbles agglomerations in the samples produced from the nanopowder. A radial gradient of temperature (decreasing from the center to the border) was observed at the compacts fabricated with the crystalline powders favoring the closure of the open porosity. The presence or the absence of non-fused material and bubbles in the samples was analyzed by X-ray diffraction, optical microscopy and density measurements. The transmittance analysis indicated an almost zero quantity of OH groups in the compacts sintered from crystalline powders and about 20 ppm in the solids fabricated from the sol-gel raw material. Nanopowder samples of silica titania (~6 wt % of titania) were processed with final temperatures of 1200°C and 1400°C presenting blue and black coloration, respectively, and an increase of the titania clusters for the highest temperature. The sintering at temperatures near 1200°C with a holding time of just 4 minutes caused the complete anatase-rutile conversion in titania.

<p>U ovom radu sintetisani su kompozitni nanoprahovi i nanoprahovi tipa jezgro&ndash; omotač sa dielektričnom i magnetnom fazom, kao pogodan polazni materijal za procesiranje kompozitne keramike za primenu u mikroelektronici. Osnovni cilj ove doktorske disertacije je bio utvrđivanje veza između uslova sinteze, morfologije čestica, uslova procesiranja i mikrostrukture kompozitne keramike. Nanoprahovi su sintetisani hemijskim metodama sinteze u tečnoj fazi (sol-gel i koprecipitacija) i gasnoj fazi (CVS), pri čemu je vr&scaron;ena optimizacija procesnih uslova u cilju sinteze čestica željene strukture i hemijskog sastava. Istraživanja su vr&scaron;ena na nekoliko modelnih sistema sa feritima kao magnetnom fazom i titanatima ili silikom kao dielektričnom fazom: NiFe2O4SiO2, Fe3O4SiO2, SrTiO3NiFe2O4, BaTiO3NiFe2O4 i BaTiO3Fe3O4. Hemijska sinteza u tečnoj fazi se pokazala pogodnom zato &scaron;to pruža mogućnost kontrolisanja morfologije kompozitnih čestica ne samo pode&scaron;avanjem procesnih parametara sinteze već i funkcionalizacijom faza kojom se uzrokuje njihovo elektrostatičko privlačenje i formiranje strukture jezgro&ndash;omotač. Ipak, zbog velikog stepena aglomeracije prisutnog tokom sinteze u tečnoj fazi, dobijanje omotača uniformne debljine i izbegavanje homogene nukleacije faza se pokazalo te&scaron;ko. Hemijskom sintezom u gasnoj fazi (CVS) je po prvi put sintetisan kompozitni nanoprah na bazi kompleksnih oksida titanata i ferita.<br />Utvrđeno je da i pored velikog potencijala CVS metode u smislu sinteze ultrafinih prahova na bazi titanata i ferita u jednom koraku, ova metoda nudi relativno slabu kontrolu morfologije kompozitnih čestica pri visokim procesnim temperaturama koje su neophodne za kristalizaciju dve faze. Sintetisani nanoprahovi na bazi titanata i ferita (SrTiO3NiFe2O4 i BaTiO3NiFe2O4) procesirani su u gustu kompozitnu keramiku visokotemperaturnim sinterovanjem, u cilju ispitivanja veze morfologije čestica i mikrostrukture kompozita, optimizacije režima sinterovanja i funkcionalne karakterizacije dobijene keramike sa različitim masenim odnosom faza. Prahovi su sinterovani putem konvencionalnog sinterovanja u atmosferi vazduha, spark plazma sinterovanja (SPS) ili kombinacijom ove dve metode. Utvrđeno je da prahovi strukture jezgro&ndash;omotač densifikuju u značajno gu&scaron;ću i homogeniju keramiku u odnosu na kompozitne prahove istog sastava na istim procesnim temperaturama. Pored toga, pH vrednost sinteze čestica i atmosfera visokotemperaturnog sinterovanja su se pokazali veoma značajnim u smislu održavanja željenog faznog sastava dobijenih kompozita. U pogledu režima sinterovanja dobijenih prahova, kombinacija niskotemperaturnog konvencionalnog i SPS sinterovanja (1000 &deg;C) je dala najbolje rezultate u smislu postizanja zadovoljavajuće gustine kompozita (&gt;95% teorijske gustine), održavanja željenog faznog sastava i homogene distribucije faza. Funkcionalna karakterizacija sinterovane keramike sa različitim masenim odnosom faza (BaTiO3 : NiFe2O4 = 1,2,8) potvrdila je očekivano dielektrično, feroelektrično i ferimagnetno pona&scaron;anje dobijenih kompozita.</p> / <p>Composite and core&ndash;shell nanopowders with dielectric and magnetic phase have been synthesized in this work, as a suitable starting material for processing of composite ceramics for microelectronic application. The main goal of this doctoral dissertation was the determination of the link between synthesis conditions, particle morphology, processing conditions and microstructure of composite ceramics. Nanopowders have been synthesized by chemical synthesis methods in wet phase (sol&ndash;gel and coprecipitation) and gas phase (CVS), whereas the optimization of processing parameters was conducted with the goal to synthesize particles of desired structure and chemical composition. Studies were conducted on the few model systems with ferrites as a magnetic and titanates as a dielectric phase: NiFe2O4SiO2, Fe3O4SiO2, SrTiO3NiFe2O4, BaTiO3NiFe2O4 and BaTiO3Fe3O4. Chemical wet synthesis has proven suitable because it offers composite particle morphology control not only by adjustment of synthesis parameters but also by phase functionalization causing their mutual electrostatic attraction and thus core&ndash;shell structure formation. However, due to the high degree of agglomeration present during the wet phase synthesis, formation of the shell with uniform thickness and avoidance of homogeneous nucleation has proven difficult. For the first time, composite ferrite and titanate-based nanopowder has been synthesized by means of Chemical Vapor Synthesis (CVS). It has been found that beside high potential of CVS method for one-step synthesis of ultrafine titanate and ferrite-based nanopowders, this method offers relatively low control of composite particle morphology at high processing temperatures which are necessary for crystallization of both phases. Synthesized titanate and ferrite-based nanopowders (SrTiO3NiFe2O4 and BaTiO3NiFe2O4) were processed into dense ceramics by high-temperature sintering, in order to find the link between particle morphology and composite microstructure, optimize the sintering regime and conduct the functional characterization of obtained ceramics with different phase mass ratio.<br />The powders were sintered by conventional sintering in air, spark plasma sintering<br />(SPS) or combination of these two methods. It was found that core&ndash;shell powders densify in ceramics with considerably higher density and homogeneity at the same processing temperature, than the composite powders with the same composition. Moreover, synthesis pH value and sintering temperature was found to be very important in terms of phase composition preservation of obtained composites. Regarding the sintering regime of obtained powders, combination of low-temperature conventional and SPS sintering (1000 &deg;C) has given the best results in terms of achieving adequate composite density (&gt;95% theoretical density), phase preservation and homogeneous phase distribution. Functional characterization of sintered ceramics with different phase mass ratio (BaTiO3 : NiFe2O4 = 1,2,8) confirmed the expected dielectric, ferroelectric and ferromagnetic behaviour of obtained composites.</p>

<p>U ovom radu su sintetisani prahovi na bazi lantan-galata, citratnom sol-gel<br />metodom i hemijskom sintezom u parnoj fazi (CVS), a njihovim presovanjem<br />i sinterovanjem su dobijeni keramički uzorci kontrolisane mikrostrukture. Cilj<br />disertacije je bio dobijanje guste keramike koja bi mogla da se primeni kao<br />jonski provodni elektrolit u gorivnim ćelijama sa čvrstim elektrolitom (SOFC),<br />a koje bi radile na srednjim temperaturama od 500&ndash;700 &deg;C (IT-SOFC). Po prvi<br />put su sintetisani nanoprahovi lantan-galata u gasnoj fazi i utvrđeno je da ovako<br />dobijeni polazni prahovi, zbog svojih superiornih karakteristika omogućavaju<br />snižavanje temperature sinterovanja za 150 &deg;C, &scaron;to je veoma povoljno kako sa<br />stanovi&scaron;ta dizajniranja mikrostrukture, tako i zbog u&scaron;tede energije u procesu<br />proizvodnje gorivnih ćelija. Ipak, zbog nedovoljne kontrole hemijskog sastava<br />i stehiometrije sintetisanih prahova, &scaron;to je i najveći nedostatak CVS metode<br />dobijanja perovskitnog LaGaO₃, nije bilo moguće dobiti keramiku koja bi ispunjavala zahteve za primenu u SOFC. S druge strane, citratna sol-gel metoda<br />pruža veliku kontrolu pomenutih parametara zbog čega je bila moguća sinteza<br />čitavog niza čvrstih rastvora lantan-galata. Ovom metodom su tako sintetisani<br />čist lantan-galat (LG) i dopirani prahovi kod kojih je deo lantana supstituisan<br />stroncijumom, a deo galijuma magnezijumom: La_0,85Sr_0,15Ga_0,85Mg_0,15O_3-<br />La_1-xSr_xGa_0,8Mg_0,2O_3-, gde je x = 0,10, 0,15 ili 0,20 (LSGM). Svi ovako sintetisani</p><p>prahovi su zahtevali naknadnu kalcinaciju na 900 &deg;C, ali su potrebne<br />gustine (&gt;95% teorijske gustine) postignute sinterovanjem na temperaturi<br />od 1450 &deg;C već nakon 2 h, &scaron;to je izuzetno kratko imajući u vidu literaturne<br />podatke. Takođe, sinterovani uzorci su po faznom sastavu bili čista LSGM<br />keramika, a impedansna merenja su pokazala da je najveću provodljivost imao<br />uzorak La_0,85Sr_0,15Ga_0,8Mg_0,2O_3-. Ovaj sastav je dalje kori&scaron;ćen u cilju provere</p><p>mogućnosti za dodatno povećanje provodljivosti te su pripremljeni i uzorci kod kojih je izvr&scaron;ena parcijalna supstitucija magnezijuma sa niklom ili kobaltom:<br />La_0,85Sr_0,15Ga_0,8Mg_0,2-yMyO_3-, gde je M = Ni ili Co, a y = 0,03 ili 0,05 (LSGMN i</p><p>LSGMC). Pokazano je da dodatak male količine prelaznih metala značajno utiče<br />na mehanizam provođenja, ali da je na vi&scaron;im temperaturama jonska provodljivost<br />i dalje dominantna. Konstatovano je da se dodavanjem male količine Ni ili Co u<br />LSGM mogu dobiti materijali koji bi služili kao elektroliti u IT-SOFC, pri čemu je<br />potencijal nikla kao dopanta ne&scaron;to veći nego kobalta.</p> / <p>Powders based on lanthanum-gallate have been synthesised in this work by using citrate sol-gel method in the liquid phase and by chemical vapour synthesis (CVS). As-synthesised powders were calcined, pressed and finally sintered in order to produce ceramic samples with controlled microstructure. The main goal of this dissertation has been obtaining of dense ceramics for application in ion conducting electrolyte for solid oxide fuel cells working at 500&ndash;700 &deg;C (IT-SOFC). Lanthanum-gallate nanopowders have been synthesised in the gas phase for the first time and it has been determined that these starting powders posses superior properties which could lower down the sintering temperature for about 150 &deg;C. This is very significant considering microstructure design, but also high energy consumption during the manufacturing process of fuel cells. However, it has not been possible to obtain ceramics with exact properties needed for SOFC application using CVS due to the lack of control of chemical composition and stoichiometry of the as-synthesised powders, which are the main drawbacks of this method. On the other hand, citrate sol-gel method offered a possibility to precisely control aforementioned parameters which enabled synthesis of a whole range of lanthanum-gallate sollid solutions. So, pure perovskite lanthanum-gallate (LG) has been synthesised by using this liquid phase method, but also doped powders where part of lanthanum and gallium was supstituted with strontium and magnesium, respectively: La_0,85Sr_0,15Ga_0,85Mg_0,15O_3-and La_1-xSr_xGa_0,8Mg_0,2O_3-, where x = 0.10, 0.15 or 0.20 (LSGM). Calcination at 900 &deg;C was necessary step during the processing of these sol-gel powders but the sintering time at 1450 &deg;C was only 2 h which is quite short in comparison with available literature data. Additionaly, the sintered samples were phase pure LSGM ceramics and impedance measurement showed that the highest conductivity had sample La_0,85Sr_0,15Ga_0,8Mg_0,2O_3-. Accordingly, this composition has been used to check the possibility of further improvement of conductivity. A set of new samples has been prepared where one part of magnesium has been substituted with nickel or cobalt: La_0,85Sr_0,15Ga_0,8Mg_0,2-yMyO_3-, where M = Ni or Co and y = 0.03 or 0.05 (LSGMN i LSGMC). It has been shown that addition of small amount of transition metals significantly influences conduction mechanism, but at higher temperatures the ionic conductivity is still dominant. It has been found that electrolyte materials for IT-SOFCs could be obtained by incorporation of small quantities of Ni or Co into LSGM and that nickel is more promissing for this purpose than cobalt.</p>

Made available in DSpace on 2014-06-11T19:25:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-18Bitstream added on 2014-06-13T18:53:40Z : No. of bitstreams: 1 rebeque_pvs_me_ilha.pdf: 2184375 bytes, checksum: 85d1dba31d0aecfc00a6316b5737526f (MD5) / Compósitos poliméricos condutores, também chamados de polímeros condutores extrínsecos, têm sido alvo de intensa pesquisa científica devido ao seu grande potencial de aplicação nos mais diversificados setores industriais. Esses materiais combinam as características de um polímero (leveza, flexibilidade, fácil processamento) com as de cargas condutoras (alta condutividade). O poliuretano derivado de óleo de mamona (PUR) é um polímero obtido pela mistura de pré-polímero e poliol (derivado de óleo de mamona) que apresenta grande potencial para ser utilizado como matriz polimérica em compósitos. Ele possui propriedades equivalentes aos dos poliuretanos (PU) convencionais e tem como vantagem ser um polímero biodegradável e proveniente de fonte renovável. Em relação às cargas condutoras, o negro de fumo (NF) é um dos materiais mais utilizados para esse fim, enquanto que pouco se encontra na literatura sobre o carvão ativado nano em pó (CANP), mesmo possuindo estrutura semelhante e maior condutividade que o NF. Neste contexto, o presente trabalho tem como objetivo viabilizar os processos de síntese e fazer a caracterização elétrica dos compósitos poliuretano derivado de óleo de mamona/carvão ativado nano em pó (PUR/CANP) e poliuretano derivado de óleo de mamona/negro de fumo (PUR/NF) na forma de filmes pelo método “casting”, mantendo fixa a razão pré-polímero/poliol e variando a fração de volume de CANP e NF. A análise térmica foi feita por Calorimetria Diferencial de Varredura (DSC), o estudo da condutividade dc e ac foram feitas pelo Método de Duas Pontas (tensão x corrente) (MDP) e pela técnica de Espectroscopia de Impedância Elétrica (EIE), respectivamente, e a análise morfológica foi feita em Microscópio Eletrônico de Varredura com canhão de elétrons por... / Conductive polymer composites, also called extrinsic conducting polymers, has been the subject of intense scientific research due to its great potential for industrial application. These materials combine the characteristics of a polymer (lightness, flexibility, easy processing) with the conductive fillers (high conductivity). The castor oil based polyurethane (PUR) is a polymer obtained from pre-polymer and polyol (based castor oil) mixing which has great potential to be used as matrix polymer in composites. It has properties equivalent to those of conventional polyurethane (PU) and has the advantage of being a biodegradable polymer and from a renewable source. In relation to conductive fillers, carbon black (CB) is one of the most widely used materials for this purpose, while in the literature there are few data about activated carbon nanopowder (ACNP), despite having similar structure and that the higher conductivity than CB. In this context, this work aims to provide the synthesis processes and electrically characterize of composite castor oil based polyurethane/activated carbon nanopowder (PUR/ACNP) and castor oil based polyurethane/carbon black (PUR/CB) in the form of films by casting, keeping the ratio pré-polímero/poliol fixed and varying the volume fraction ACNP and CB. The sample were characterized using Differential Scanning Calorimetry (DSC), Two Points Method (voltage x current) (TPM), Electrical Impedance Spectroscopy (EIS) and Scanning Electron Microscope with electron gun for field emission (FEG-SEM). DSC results showed that the glass transition temperature (Tg) of composites do not depend of type or volume fraction of conductive fillers. The results of electrical analysis showed that the samples of PUR/CB have lower percolation threshold than those of PUR/ACNP (20% vs. 40%). This result is due the distribution... (Summary complete electronic access click below)